Geotectonic vs. Anthropogenic Drivers of Environmental Changes in the Basins of lakes Naivasha and Elmenteita (East Africa)

• Applicants: Dr. Annett Junginger; Privatdozent Dr. Simon Kübler
• Subject Area: Geology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547402363

The lake basins in the East African Rift System (EARS) are vital ecological and biological reservoirs that are currently facing critical challenges due to natural and anthropogenic pressures. An important role plays here the change in the chemical composition of these lakes due to the input of pollutants, either from anthropogenic waste (e.g., fuel emissions, sewage, fertilizers) or from the natural geological components of their catchment area itself. Extensive agriculture and urbanization, but also natural, tectonic processes, can expose soils and rocks with their sometimes-toxic components and transport them into the lakes, disturbing the natural balance and changing the lake biota. To decipher the natural from anthropogenic drivers of such environmental changes in an area with simultaneously fast-growing population and complex geology such as the EARS, we propose a pilot study on Lakes Elmenteita and Naivasha in the central Kenya Rift. These two lakes are of particular interest as they show strong differences in their hydrochemical compositions despite their close proximity (~30 km), similar population growth dynamics in recent decades and shared geological and climatic characteristics. This makes the two lakes ideal study sites to investigate the interplay between natural and human processes on two different aquatic ecosystems under the same basic conditions. Using an interdisciplinary "source to sink" approach, we will investigate the catchment of these two lakes for tectonic geomorphology, soils, rocks, hydrology, anthropogenic debris and biology (esp. diatoms, vegetation). The analysis of lake sediments from cores of both lakes will serve to reveal changes in the vegetation (via pollen and phytoliths) of the catchment area, the sediment provenance and chemistry as well as its influence on the diatoms as sensitive indicators of changes in lake chemistry over the last decades. For the determination of the chemical composition of the collected samples we focus on elemental composition, Zn-Pb isotopes, major oxides, trace elements and TOC. The use of advanced remote sensing techniques will complete the look into the past by tracing land use changes in the catchments back to the early 1980s and assessing their impact on the state and dynamics of the lakes. By incorporating a citizen science approach, the study will also collect local knowledge to enhance our understanding of historical and current changes in the catchments. This multi-faceted approach not only aims to separate natural from anthropogenic influences on the sensitive lake systems of the EARS, but also provides crucial insights into the mechanisms by which human activities are reshaping these critical ecosystems and provides a basis and guidance for the study of other vulnerable lake systems.

• DFG Programme: Research Grants
• International Connection: Kenya, Spain
• Cooperation Partners: Dr. Veronica Mwihaki Muiruri; Dr. Carolina Rosca